Docs: Exclude decorators by default from source

[tmeasday]

What I did

Due to reordering in #21182 the source decorator comes before any user decorator in preview.js. This means that we commonly trigger the bug in #21649.

Really it was a bug that was fixed by #21182 that the user's decorators weren't visible in the source by default given we weren't excluding them.

So it makes more sense to default this to true and people can opt out in cases where they want to show the decorator.

How to test

Add the following to a React sandbox's preview.tsx:

  decorators: [
    (S) => <div><S/></div>
  ]

Then check the source block of a story:

Checklist

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests)
• Make sure to add/update documentation regarding your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Maintainers

• If this PR should be tested against many or all sandboxes,
  make sure to add the ci:merged or ci:daily GH label to it.
• Make sure this PR contains one of the labels below.

["cleanup", "BREAKING CHANGE", "feature request", "bug", "documentation", "maintenance", "dependencies", "other"]

[tmeasday]

We also might want to consider doing this for React only, as I think that's the only place the issue likely happens (see #21649 (comment)).

However, I think it's reasonable to exclude decorators by default everywhere.

[shilman]

Aside from some markdown issues LGTM. Thanks @tmeasday !

Solved